Organic light emitting diode display device and method of fabricating the same

ABSTRACT

In an organic light emitting diode (OLED) display device and a method for fabricating the same, OLED pixels are patterned through a photolithography process, so a large area patterning can be performed and a fine pitch can be obtained, and an organic compound layer can be protected by forming a buffer layer of a metal oxide on an upper portion of the organic compound layer or patterning the organic compound layer by using a cathode as a mask, improving device efficiency. In addition, among red, green, and blue pixels, two pixels are patterned through a lift-off process and the other remaining one is deposited to be formed without patterning, the process can be simplified and efficiency can be increased.

CROSS REFERENCE TO RELATED APPLICATION

The application is a Divisional of U.S. patent application Ser. No.13/624,166, filed on Sep. 21, 2012, which claims the benefit of KoreanApplications No. 10-2011-0095959, filed on Sep. 22, 2011, and No.10-2012-0101196, filed on Sep. 12, 2012, which are herein expresslyincorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to organic light emitting diode (OLED)display device and a method of fabricating the same and, moreparticularly, to an OLED display device in which OLED pixels arepatterned through a photolithography process, and a method offabricating the same.

DESCRIPTION OF THE RELATED ART

Recently, as interest in information displays has been on the rise anddemand for the use of portable information media has been increased,lightweight flat panel displays (FPDs) substituting cathode ray tubes(CRTs) as existing display devices have been actively researched andcommercialized.

In the FPD fields, a liquid crystal display (LCD) device, which islighter and consumes less power, has been spotlighted; however, since anLCD device is a light receiving device, rather than a light emittingdevice, having shortcomings of brightness, contrast ratio, and a viewingangle, and the like, so a development of a new display device that mayovercome such drawbacks has been actively made.

An LED display device, one of new display devices, is a self-luminoustype device, which thus is excellent in a viewing angle and contrastratio, is lighter and thinner because it does not need a backlight, andis advantageous in terms of power consumption, relative to an LCDdevice. In addition, an OLED display device can be driven by a DC and ata low voltage, has a fast response speed, and is especially advantageousin terms of fabrication costs.

Unlike an LCD device or a plasma display panel (PDP), deposition andencapsulation are the whole of a fabrication process of an OLED displaydevice, so the fabrication process is very simple. Also, when the OLEDdisplay device is driven according to an active matrix scheme in whicheach pixel has a thin film transistor (TFT) as a switching element, thesame luminance can be obtained although a low current is applied, so,advantageously, the OLED display device consumes low power, has a highpitch (or high definition or high resolution), and can be increased insize.

Hereinafter, a basic structure and operational characteristics of anOLED display device will be described in detail with reference to theaccompanying drawings.

FIG. 1 is a diagram illustrating a light emission principle of a generalOLED display device.

As shown in FIG. 1, a general OLED display device includes an OLED. TheOLED includes organic compound layers 301, 30 b, 30 c, 30 d, and 30 eformed between an anode 18 as a pixel electrode and a cathode 28 as acommon electrode.

Here, the organic compound layers 30 a, 30 b, 30 c, 30 d, and 30 einclude a hole injection layer 30 a, a hole transport layer 30 b, anemission layer 30 c, an electron transport layer 30 d, and an electroninjection layer 30 e.

When a driving voltage is applied to the anode 18 and the cathode 28,holes which have passed through the hole transport layer 30 b andelectrons which have passed through the electron transport layer 30 emove to the light emission layer 30 c to form excitons, and as a result,the light emission layer 30 c emits visible light.

In the OLED display device, the pixels each having the OLED having theforegoing structure are arranged in a matrix form and selectivelycontrolled by a data voltage and a scan voltage to display an image.

The OLED display device is divided into a passive matrix type OLEDdisplay device and an active matrix type display device using TFTs asswitching elements. Among them, in the active matrix type OLED displaydevice, TFTs as active elements are selectively turned on to selectpixels and emitting of pixels is maintained by a voltage maintained in astorage capacitor.

FIG. 2 is an equivalent circuit diagram of a pixel in a general OLEDdisplay device. Namely, FIG. 2 illustrates an example of an equivalentcircuit diagram of a pixel having a general 2T1C (including twotransistors and one capacitor) in an active matrix type OLED displaydevice.

Referring to FIG. 2, a pixel of an active matrix type OLED displaydevice includes an OLED, a data line DL and a gate line GL crossing eachother, a switching TFT SW, a driving TFT DR, and a storage capacitorCst.

Here, the switching TFT SW is turned on in response to a scan pulse fromthe gate line GL to conduct a current path between a source electrodeand a drain electrode thereof. During an ON-time period of the switchingTFT SW, a data voltage from the data line DL is applied to a gateelectrode of the driving TFT DR and the storage capacitor Cst by way ofthe source electrode and drain electrode of the switching TFT SW.

Here, the driving TFT DR controls a current flowing in the OLEDaccording to the data voltage applied to the gate electrode thereof. Thestorage capacitor Cst stores a voltage between the data voltage and alow potential power source voltage VSS and uniformly maintains it duringone frame period.

In order to form the several organic compound layers constituting theOLED display device, a vacuum evaporation method is largely used.

Here, in order to use the vacuum evaporation method, a mask (or a shadowmask) or a fine metal mask (FMM) having a plurality of openingscorresponding to a plurality of pixel regions is used. However, thismethod has a limitation in that it is not easy to cope with a fine pitchof patterns for increasing a size of a substrate and implementing a highresolution display

Namely, FMM is fabricated by forming holes as a pattern intended fordeposition on a thin metal plate and stretching the same. Thus, there isa limitation in forming a pattern having a small size, making itdifficult to reduce the size of an OLED. Also, when a fine metal mask isincreased in size in order to increase a size of a panel, warpage occursdue to the characteristics of the fine metal mask, distort the patternto degrade a production yield.

SUMMARY OF THE INVENTION

An aspect of the present invention provides an organic light emittingdiode (OLED) display device in which OLED pixels are patterned through aphotolithography process, thus being available for large area patterningand obtaining a high pitch (or high definition or high resolution), anda method for fabricating the same.

Another aspect of the present invention provides an OLED display devicein which a light emitting layer is protected during a patterning processthrough photolithography, and a method for fabricating the same.

Another aspect of the present invention provides an OLED display devicecapable of simplifying a process and increasing efficiency, and a methodfor fabricating the same.

According to an aspect of the present invention, there is provided anorganic light emitting diode (OLED) display device including: a firstelectrode formed on a substrate; a hole injection layer and a holetransport layer formed on the substrate with the first electrode formedthereon; a first light emitting layer formed of a first organic film onthe substrate with the hole injection layer and the hole transport layerformed thereon; a second light emitting layer formed of a second organicfilm on the substrate with the first light emitting layer formedthereon; a third light emitting layer formed by depositing a thirdorganic film on the entire surface of the substrate with the first lightemitting layer and the second light emitting layer formed thereon; andan electron injection layer and a second electrode formed on the thirdlight emitting layer.

The third light emitting layer may be formed on upper portions of thefirst light emitting layer and the second light emitting layer as wellas between the first light emitting layer and the second light emittinglayer.

According to another aspect of the present invention, there is providedan organic light emitting diode (OLED) display device including: a firstelectrode formed on a substrate; a first hole injection layer, a firsthole transport layer, a first light emitting layer, a first electrontransport layer, and a first buffer layer laminated on the substrate; asecond hole injection layer, a second hole transport layer, a secondlight emitting layer, a second electron transport layer, and a secondbuffer layer laminated on the substrate; a third hole injection layer, athird hole transport layer, a third light emitting layer, a thirdelectron transport layer, and a third buffer layer laminated on thesubstrate; and a second electrode formed on the first, second, and thirdbuffer layers, wherein the first, second, and third buffer layers aremade of a metal oxide.

The first, second, and third buffer layers may be made of a 1-2 Groupand 12-16 Group metal oxide or 3-12 Group transition metal oxide.

According to another aspect of the present invention, there is provideda method for fabricating an organic light emitting diode (OLED) displaydevice, including: forming a first electrode on a substrate; forming afirst light emitting layer formed of a first organic film on thesubstrate through a first photo process; forming a second light emittinglayer formed of a second organic film on the substrate through a secondphoto process; depositing a third organic film on first and secondphotosensitive resin patterns remaining after being used during thefirst and second photo processes; removing the third organic filmdeposited on upper portions of the first and second photosensitive resinpatterns together with the first and second photosensitive resinpatterns through a lift-off process to form a third light emittinglayer; and forming a second electrode on the first, second, and thirdlight emitting layers.

According to another aspect of the present invention, there is provideda method for fabricating an organic light emitting diode (OLED) displaydevice, including: (a) forming a first electrode on a substrate; (b)applying a photosensitive resin to the entire surface of the substrateto form a first photosensitive resin layer; (c) selectively exposing anddeveloping the first photosensitive resin layer to form a firstphotosensitive resin pattern made of the photosensitive resin at aposition other than a position where a first light emitting layer is tobe formed; (d) depositing a first organic film on the firstphotosensitive resin pattern in a state in which the firstphotosensitive resin pattern remains; (e) removing the first organicfilm deposited on an upper portion of the first photosensitive resinpattern together with the first photosensitive resin pattern through alift-off process to form a first light emitting layer formed of thefirst organic film on the substrate; (f) forming a second light emittinglayer formed of a second organic film on the substrate through the sameprocesses as (b) to (e); (g) depositing a third organic film on theentire surface of the substrate with the first light emitting layer andthe second light emitting layer formed thereon; and (h) forming a secondelectrode on the substrate.

The third light emitting layer may be formed between the first lightemitting layer and the second light emitting layer.

The third light emitting layer may be formed on upper portions of thefirst light emitting layer and the second light emitting layer as wellas between the first light emitting layer and the second light emittinglayer.

After a hole injection layer and a hole transport layer are formed onthe substrate with the first electrode formed thereon, the first lightemitting layer may be formed thereon.

The first light emitting layer may be formed as any one of red, green,and blue light emitting layers.

The second light emitting layer may be formed as another one of the red,green, and blue light emitting layers.

The third light emitting layer may be formed as the other remaining oneof the red, green, and blue light emitting layers.

After an electron transport layer and an electron injection layer areformed on the substrate with the first, second, and third light emittinglayers formed thereon, the second electrode may be formed thereon.

According to another aspect of the present invention, there is provideda method for fabricating an organic light emitting diode (OLED) displaydevice, including: forming a first electrode on a substrate; forming afirst hole injection layer, a first hole transport layer, a first lightemitting layer, a first electron transport layer, and a first bufferlayer in a laminated manner on the substrate through a first photoprocess; forming a second hole injection layer, a second hole transportlayer, a second light emitting layer, a second electron transport layer,and a second buffer layer in a laminated manner on the substrate througha first photo process; forming a third hole injection layer, a thirdhole transport layer, a third light emitting layer, a third electrontransport layer, and a third buffer layer in a laminated manner on thesubstrate through a first photo process; and forming a second electrodeon the first, second, and third buffer layers, wherein the first,second, and third buffer layers are made of a metal oxide.

According to another aspect of the present invention, there is provideda method for fabricating an organic light emitting diode (OLED) displaydevice, including: (a) forming a first electrode on a substrate; (b)applying a photosensitive resin to the entire surface of the substrateto form a first photosensitive resin layer; (c) selectively exposing anddeveloping the first photosensitive resin layer to form a firstphotosensitive resin pattern made of the photosensitive resin at aposition other than a position where a first light emitting layer is tobe formed; (d) depositing a thin film for a first hole injection layer,a thin film for a first hole transport layer, a first organic film, athin film for a first electron transport layer, and a thin film for afirst buffer layer in a state in which the first photosensitive resinpattern remains; (e) removing the thin film for a first hole injectionlayer, the thin film for a first hole transport layer, the first organicfilm, the thin film for a first electron transport layer, and the thinfilm for a first buffer layer deposited on an upper portion of the firstphotosensitive resin pattern together with the first photosensitiveresin pattern through a lift-off process to form a first hole injectionlayer, a first hole transport layer, a first light emitting layer, afirst electron transport layer, and a first buffer layer, which areformed of thin film for a first hole injection layer, the thin film fora first hole transport layer, the first organic film, the thin film fora first electron transport layer, and the thin film for a first bufferlayer, respectively, on the substrate; (f) forming a second holeinjection layer, a second hole transport layer, a second light emittinglayer, a second electron transport layer, and a second buffer layerthrough the same processes as (b) to (e); (g) forming a third holeinjection layer, a third hole transport layer, a third light emittinglayer, a third electron transport layer, and a third buffer layerthrough the same processes as (b) to (e); and (h) forming a secondelectrode on the first, second, and third buffer layers, wherein thefirst, second, and third buffer layers are made of a metal oxide.

The forming of the first hole injection layer, the first hole transportlayer, the first light emitting layer, the first electron transportlayer, and the first buffer layer may include: depositing a thin filmfor a first hole injection layer, a thin film for a first hole transportlayer, a first organic film, a thin film for a first electron transportlayer, and a thin film for a first buffer layer on the substrate;applying a photosensitive resin to the entire surface of the substratewith the thin film for a first hole injection layer, the thin film for afirst hole transport layer, the first organic film, the thin film for afirst electron transport layer, and the thin film for a first bufferlayer deposited thereon to form a first photosensitive resin layer;exposing and developing the first photosensitive resin layer to from afirst photosensitive resin pattern made of the photosensitive resin at aposition where a first light emitting is to be formed; and selectivelyetching the thin film for a first hole injection layer, the thin filmfor a first hole transport layer, the first organic film, the thin filmfor a first electron transport layer, and the thin film for a firstbuffer layer by using the first photosensitive resin pattern as a maskto form the first hole injection layer, the first hole transport layer,the first light emitting layer, the first electron transport layer, andthe first buffer layer, which are formed of thin film for a first holeinjection layer, the thin film for a first hole transport layer, thefirst organic film, the thin film for a first electron transport layer,and the thin film for a first buffer layer, respectively, on thesubstrate.

The forming of the second hole injection layer, the second holetransport layer, the second light emitting layer, the second electrontransport layer, and the second buffer layer may include: depositing athin film for a second hole injection layer, a thin film for a secondhole transport layer, a second organic film, a thin film for a secondelectron transport layer, and a thin film for a second buffer layer onthe substrate; applying a photosensitive resin to the entire surface ofthe substrate with the thin film for a second hole injection layer, thethin film for a second hole transport layer, the second organic film,the thin film for a second electron transport layer, and the thin filmfor a second buffer layer deposited thereon to form a secondphotosensitive resin layer; exposing and developing the secondphotosensitive resin layer to from a second photosensitive resin patternmade of the photosensitive resin at a position where a second lightemitting is to be formed; and selectively etching the thin film for asecond hole injection layer, the thin film for a second hole transportlayer, the second organic film, the thin film for a second electrontransport layer, and the thin film for a second buffer layer by usingthe second photosensitive resin pattern as a mask to form the secondhole injection layer, the second hole transport layer, the second lightemitting layer, the second electron transport layer, and the secondbuffer layer, which are formed of thin film for a second hole injectionlayer, the thin film for a second hole transport layer, the secondorganic film, the thin film for a second electron transport layer, andthe thin film for a second buffer layer, respectively, on the substrate.

The forming of the third hole injection layer, the third hole transportlayer, the third light emitting layer, the third electron transportlayer, and the third buffer layer may include: depositing a thin filmfor a third hole injection layer, a thin film for a third hole transportlayer, a third organic film, a thin film for a third electron transportlayer, and a thin film for a third buffer layer on the substrate;applying a photosensitive resin to the entire surface of the substratewith the thin film for a third hole injection layer, the thin film for athird hole transport layer, the third organic film, the thin film for athird electron transport layer, and the thin film for a third bufferlayer deposited thereon to form a third photosensitive resin layer;exposing and developing the third photosensitive resin layer to from athird photosensitive resin pattern made of the photosensitive resin at aposition where a third light emitting is to be formed; and selectivelyetching the thin film for a third hole injection layer, the thin filmfor a third hole transport layer, the third organic film, the thin filmfor a third electron transport layer, and the thin film for a thirdbuffer layer by using the third photosensitive resin pattern as a maskto form the third hole injection layer, the third hole transport layer,the third light emitting layer, the third electron transport layer, andthe third buffer layer, which are formed of thin film for a third holeinjection layer, the thin film for a third hole transport layer, thethird organic film, the thin film for a third electron transport layer,and the thin film for a third buffer layer, respectively, on thesubstrate.

The first, second, and third buffer layers may be made of a 1-2 Groupand 12-16 Group metal oxide or 3-12 Group transition metal oxide.

According to another aspect of the present invention, there is provideda method for fabricating an organic light emitting diode (OLED) displaydevice, including: (a) forming a fourth electrode on a substrate; (b)forming a first organic film and a first conductive film on thesubstrate with the fourth electrode formed thereon; (c) applying aphotosensitive resin to the entire surface of the substrate with thefirst conductive film formed thereon to form a first photosensitiveresin layer; (d) selectively exposing and developing the firstphotosensitive resin layer to form a first photosensitive resin patternmade of the photosensitive resin at a position at which a first lightemitting is to be formed; (e) selectively removing the first conductivefilm by using the first photosensitive resin pattern as a mask to form afirst electrode; (f) removing the first photosensitive resin pattern andselectively removing the underlying exposed first organic film by usingthe first electrode as a mask to form a first light emitting layerformed of the first organic film; (g) forming a second light emittinglayer and a second electrode on the substrate through the same processesas (b) to (f); and (h) forming a third light emitting layer and a thirdelectrode on the substrate through the same processes as (b) to (f).

After a thin film for a first hole injection layer and a thin film for afirst hole transport layer are formed on the substrate with the fourthelectrode formed thereon, the first organic film may be formed, andafter a thin film for a first electron transport layer is formed, thefirst conductive film may be formed.

As described above, in the case of the OLED display device and themethod for fabricating the same according to embodiments of the presentinvention, since OLED pixels are patterned through a photolithographyprocess, a large area patterning can be performed and a fine pitch canbe obtained, and an organic compound layer can be protected by forming abuffer layer of a metal oxide on an upper portion of the organiccompound layer or patterning the organic compound layer by using acathode as a mask, improving device efficiency. Here, patterning througha photolithography process can be performed through a solution process,and since a light emitting layer is protected during a patterningprocess, a driving voltage and power consumption of the device can bereduced and efficiency can be enhanced.

Also, in the case of the OLED display device and the method forfabricating the same according to embodiments of the present invention,among red, green, and blue pixels, two pixels are patterned through alift-off process and the other remaining one is deposited to be formedwithout patterning, the process can be simplified and efficiency can beincreased.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a light emission principle of a generalorganic light emitting diode (OLED) display device.

FIG. 2 is an equivalent circuit diagram of a pixel in a general OLEDdisplay device.

FIGS. 3A through 3L are sequential sectional views illustrating a methodfor fabricating an OLED display device according to a first embodimentof the present invention.

FIGS. 4A through 4H are sequential sectional views illustrating a methodfor fabricating an OLED display device according to a second embodimentof the present invention.

FIGS. 5A through 5G are sequential sectional views illustrating a methodfor fabricating an OLED display device according to a third embodimentof the present invention.

FIG. 6 is a graph showing a state in which a life span of a device isshortened after a photolithography process is performed.

FIGS. 7A through 7K are sequential sectional views illustrating a methodfor fabricating an OLED display device according to a fourth embodimentof the present invention.

FIG. 8 is a sectional view showing another example of an OLED displaydevice fabricated according to the fourth embodiment of the presentinvention illustrated in FIGS. 7A through 7K.

FIG. 9 is a sectional view showing another example of an OLED displaydevice fabricated according to the fourth embodiment of the presentinvention illustrated in FIGS. 7A through 7K.

FIGS. 10A through 10H are sequential sectional views illustrating amethod for fabricating an OLED display device according to a fifthembodiment of the present invention.

FIGS. 11A through 11H are sequential sectional views illustrating amethod for fabricating an OLED display device according to a sixthembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, an organic light emitting diode (OLED) display device and amethod for fabricating the same according to embodiments of the presentinvention will be described in detail with reference to the accompanyingdrawings such that they can be easily implemented by a person skilled inthe art to which the present invention pertains. The present inventionmay be implemented in various forms without being limited to theembodiments described herein. Patterning of a large area with respect toan organic compound layer of an OLED display device cannot be handled byan existing method using a fine metal mask due to sagging of a substrateand a mask, so various large area patterning methods have beenresearched. Among them, the present invention proposes a patterningmethod through a photolithography process (referred to as a ‘photoprocess’, hereinafter), and here, the photo process is advantageous inthat it is available for large area patterning and obtaining a finepitch, and available for an application of a solution process.

FIGS. 3A through 3L are sequential sectional views illustrating a methodfor fabricating an OLED display device according to a first embodimentof the present invention, in which a method for fabricating an OLEDdiode with respect to some pixels is taken as an example.

Here, a method for fabricating an OLED with respect to a pixel including2T1C (two transistors and one capacitor) is taken as an example for thedescription purpose, but the present invention is not limited thereto.

First, although not shown, in an OLED display device according to afirst embodiment of the present invention, a gate line including a firstgate electrode and a storage electrode including a second gate electrodemay be formed on a substrate 110 made of an insulating material such astransparent glass, plastic, or the like.

A gate insulating layer made of silicon nitride (SiNx), silicon oxide(SiO₂), or the like, may be formed on the gate line including the firstgate electrode and the storage electrode including the second electrode.

A first active layer and a second active layer, made of semiconductor,may be formed on the gate insulating layer. The first active layer andthe second active layer may be positioned on the first gate electrodeand the second gate electrode, respectively.

A data line, a driving voltage line, a first source/drain electrode, anda second source/drain electrode may be formed on an upper portion of thefirst active layer and the second active layer.

A predetermined passivation layer may be formed on the substrate 110 onwhich the data line, the driving voltage line, the first source/drainelectrode, and the second source/drain electrode have been formed.

As shown in FIG. 3A, a pixel electrode 120 and a connecting electrode(not shown) may be formed on the substrate 110 with the passivation filmformed thereon. The pixel electrode 120 and the connecting electrode maybe made of a transparent conductive material such as indium tin oxide(ITO) or a reflective conductive material such as aluminum, silver, oran alloy thereof.

The pixel electrode 120 as an anode may be electrically connected to thesecond drain electrode through a second contact hole, and the connectingelectrode may electrically connect the first drain electrode and thesecond gate electrode through a first contact hole and a third contacthole.

A partition (not shown) may be formed on the substrate 110 with thepixel electrode 120 formed thereon. Here, the partition may encompassthe edges of the pixel electrode 120, like a bank, to define an opening,and may be made of an organic insulating material or an inorganicinsulating material.

An organic compound layer may be formed on the substrate 110.

Here, the organic compound layer may have a multilayer structureincluding an auxiliary layer in order to enhance luminous efficiency ofa light emitting layer that emits light, besides the light emittinglayer. The auxiliary layer may include an electron transport layer and ahole transport layer for balancing electrons and holes and an electroninjection layer and a hole injection layer for strengthening injectionof electrons and holes.

The organic compound layer may be formed through a photo process and alift-off process, and to this end, as shown in FIG. 3B, a first organicfilm 151 is deposited on the substrate 110.

Here, the first organic film 151 may be deposited after the holeinjection layer and the hole transport layer are formed on the substrate110, and here, the first organic film 151 may be deposited to form ared, green, or blue light emitting layer.

The hole injection layer may facilitate injection of holes from thepixel electrode 120, and the hole transport layer serves to allow holesto be transported to the light emitting layer.

Thereafter, as shown in FIG. 3C, a photosensitive resin (or photoresist)is coated on the entire surface of the substrate 110 with the firstorganic film 151 deposited thereon, to form a first photosensitive resinlayer 191.

Ultraviolet rays are selectively irradiated (exposure) to the firstphotosensitive resin layer 191 through a certain mask (not shown).

Thereafter, when the first photosensitive resin layer 191 exposedthrough the mask is developed, a first photosensitive resin pattern 190a made of the photosensitive resin remains only at a position where afirst light emitting layer is to be formed as shown in FIG. 3D.

A photosensitive resin developing solution is used for the developingoperation, and here, any developing solution may be used as long as itdoes not dissolve a material of the light emitting layer. For example, agenerally used organic alkali-based developing solution may be used, oran inorganic alkali-based developing solution or an aqueous solutioncapable of developing resist may be used.

Thereafter, as shown in FIG. 3E, a partial region of the first organicfilm formed under the first photosensitive resin pattern 190 a isselectively etched by using the first photosensitive resin pattern 190 aas a mask, to form a first light emitting layer 150 a formed of thefirst organic film on the substrate 110 (first photo process).

Here, for example, the first light emitting layer 150 a may be a redlight emitting layer, and the etching may include wet etching as well asdry etching. However, the present invention is not limited thereto andthe first light emitting layer 150 a may be a red or blue light emittinglayer.

Thereafter, as shown in FIG. 3F, with the first photosensitive resinpattern 190 a remaining, a second organic film 152 is deposited thereon.

A follow-up process is substantially the same as the first photo processfor forming the first light emitting layer 150 a. Namely, as shown inFIG. 3G, a photosensitive resin is coated on the entire surface of thesubstrate 110 with the second organic film 152 formed thereon, to form asecond photosensitive resin layer 192.

Thereafter, UV rays are selectively irradiated to the secondphotosensitive resin layer 192 through a certain mask (not shown).

Thereafter, when the second photosensitive resin layer 192 exposedthrough the mask is developed, a second photosensitive resin pattern 190b made of the photosensitive resin remains only at a position where asecond light emitting layer is to be formed as shown in FIG. 3H.

Thereafter, as shown in FIG. 3I, a partial region of the first organicfilm formed under the second photosensitive resin pattern 190 b isselectively etched by using the second photosensitive resin pattern 190b as a mask, to form a second light emitting layer 150 b formed of thesecond organic film on the substrate 110 (second photo process).

Here, for example, the second emitting layer 150 b may be a green lightemitting layer, and the etching may include wet etching as well as dryetching. However, the present invention is not limited thereto and whenthe first light emitting layer 150 a is a red light emitting layer, thesecond light emitting layer 150 b may be a blue light emitting layer,other than a green light emitting layer.

Thereafter, as shown in FIG. 3J, with the first photosensitive resinpattern 190 a and the second photosensitive resin pattern 190 bremaining, a third organic film 153 is deposited thereon.

As a follow-up process, a lift-off process, rather than a photo processsuch as the first and second photo processes as described above, isused. Namely, as shown in FIG. 3K, the first photosensitive resinpattern and the second photosensitive resin pattern are removed througha lift-off process, and here, the third organic film remaining on upperportions of the first light emitting layer 150 a and the second lightemitting layer 150 b is removed along with the first photosensitiveresin pattern and the second photosensitive resin pattern.

As a result, a third light emitting layer 150 c formed of the thirdorganic film is formed between the first light emitting layer 150 a andthe second light emitting layer 150 b.

Here, for example, when the first light emitting layer 150 a is a redlight emitting layer and the second light emitting layer 150 b is agreen light emitting layer, the third light emitting layer 150 c may bea blue light emitting layer. Also, when the first light emitting layer150 a is a red light emitting layer and the second light emitting layer150 b is a blue light emitting layer, the third light emitting layer 150c may be a green light emitting layer. However, the present invention isnot limited thereto and the first light emitting layer 150 a, the secondlight emitting layer 150 b, and the third light emitting layer 150 c maybe configured as red, green, and blue light emitting layers irrespectiveof order.

Thereafter, as shown in FIG. 3L, a common electrode 180 as a cathode maybe formed on the first light emitting layer 150 a, the second lightemitting layer 150 b, and the third light emitting layer 150 c. Here,the common electrode, which receives a common voltage, may be made of areflective conductive material including calcium (Ca), barium (Ba),magnesium (Mg), aluminum (Al), silver (Ag), or the like, or atransparent conductive material such as ITO, IZO, or the like.

Here, the foregoing common electrode 180 may be formed after theelectron transport layer and the electron injection layer are formed onthe substrate 110.

The electron injection layer facilitates injection of electrons from thecommon electrode 180, and the electron transport layer serves to allowelectrons to move to the light emitting layers 150 a, 150 b, and 150 c.

In this manner, in the case of the first embodiment of the presentinvention, since a single photo process, namely, a single photosensitiveresin coating, exposing, developing, and etching process (a total offour processes) may be omitted, and thus, the process can be simplified.Also, since OLED pixels are patterned through the photo process, largepatterning can be performed and high pitch can be obtained, and inaddition, a solution process can be performed.

In the OLED display device configured as described above, the first gateelectrode connected to the gate line and the first source electrode andthe first drain electrode connected to the data line may constitute afirst switching thin film transistor (TFT) along with the first activelayer. Also, the second gate electrode connected to the first drainelectrode, the second source electrode connected to the driving voltageline, and the second drain electrode connected to the pixel electrode120 may constitute a driving TFT along with the second active layer.

Also, the pixel electrode 120, the light emitting layers 150 a, 150 b,and 150 c, and the common electrode 180 may constitute an OLED, and themutually overlapping storage electrode and driving voltage line mayconstitute a storage capacitor.

However, as mentioned above, when the organic compound layer ispatterned through the photo process, the organic compound layer may belikely to be damaged by a photosensitive resin, a developing solution,and a strip solution, which may result in a degradation of efficiencyand a life span.

Thus, in case of second and third embodiments of the present invention,a buffer layer made of metal oxide is formed on an upper portion of theorganic compound layer to protect the organic compound layer against aphoto process. This will be described in detail with reference to theaccompanying drawings.

FIGS. 4A through 4H are sequential sectional views illustrating a methodfor fabricating an OLED display device according to a second embodimentof the present invention, in which a method for fabricating an OLEDdiode with respect to some pixels is taken as an example.

Although not shown, as mentioned above, in an OLED display deviceaccording to a second embodiment of the present invention, a gate lineincluding a first gate electrode and a storage electrode including asecond gate electrode may be formed on a substrate 210 made of aninsulating material such as transparent glass, plastic, or the like.

A gate insulating layer made of silicon nitride (SiNx), silicon oxide(SiO₂), or the like, may be formed on the gate line including the firstgate electrode and the storage electrode including the second electrode.

A first active layer and a second active layer, made of semiconductor,may be formed on the gate insulating layer. The first active layer andthe second active layer may be positioned on the first gate electrodeand the second gate electrode, respectively.

A data line, a driving voltage line, a first source/drain electrode, anda second source/drain electrode may be formed on an upper portion of thefirst active layer and the second active layer.

A predetermined passivation layer may be formed on the substrate 210 onwhich the data line, the driving voltage line, the first source/drainelectrode, and the second source/drain electrode have been formed.

As shown in FIG. 4A, a pixel electrode 220 and a connecting electrode(not shown) may be formed on the substrate 210 with the passivation filmformed thereon. The pixel electrode 220 and the connecting electrode maybe made of a transparent conductive material such as indium tin oxide(ITO) or a reflective conductive material such as aluminum, silver, oran alloy thereof.

The pixel electrode 220 as an anode may be electrically connected to thesecond drain electrode through a second contact hole, and the connectingelectrode may electrically connect the first drain electrode and thesecond gate electrode through a first contact hole and a third contacthole.

A partition (not shown) may be formed on the substrate 210 with thepixel electrode 220 formed thereon. Here, the partition may encompassthe edges of the pixel electrode 220, like a bank, to define an opening,and may be made of an organic insulating material or an inorganicinsulating material.

An organic compound layer may be formed on the substrate 210.

Here, the organic compound layer may have a multilayer structureincluding an auxiliary layer in order to enhance luminous efficiency ofa light emitting layer that emits light, besides the light emittinglayer. The auxiliary layer may include an electron transport layer and ahole transport layer for balancing electrons and holes and an electroninjection layer and a hole injection layer for strengthening injectionof electrons and holes.

Namely, as shown in FIG. 4A, a thin film 231 for a first hole injectionlayer, a thin film 241 for a first hole transport layer, a first organicfilm 251, a thin film 261 for a first electron transport layer, and athin film 271 for a first buffer layer are sequentially deposited on thesubstrate 210 with the pixel electrode 220 formed thereon.

Here, the thin film 261 for a first electron transport layer may includea thin film for a first electron injection layer, and the thin film 271for a first buffer layer may be made of a 1-2 Group and 12-16 Groupmetal oxide or 3-12 Group transition metal oxide.

Thereafter, as shown in FIG. 4B, a photosensitive resin is coated on theentire surface of the substrate 210 on which the thin film 231 for afirst hole injection layer, the thin film 241 for a first hole transportlayer, the first organic film 251, the thin film 261 for a firstelectron transport layer, and the thin film 271 for a first buffer layerare deposited, in order to form a first photosensitive resin layer 291.

UV light is selectively irradiated to the first photosensitive resinlayer 291 through a certain mask (not shown).

Thereafter, when the first photosensitive resin layer 291 exposedthrough the mask is developed, a first photosensitive resin pattern 290a made of the photosensitive resin remains only at a position where afirst light emitting layer is to be formed as shown in FIG. 4C.

Thereafter, as shown in FIG. 4D, partial regions of the thin film for afirst hole injection layer, the thin film for a first hole transportlayer, the first organic film, the thin film for a first electrontransport layer, and the thin film for a first buffer layer formed underthe first photosensitive resin pattern 290 a are selectively etched byusing the first photosensitive resin pattern 290 a as a mask, in orderto form a first hole injection layer 230 a, a first hole transport layer240 a, a first light emitting layer 250 a, a first electron transportlayer 260 a, and a first buffer layer 270 a formed of the thin film fora first hole injection layer, the thin film for a first hole transportlayer, the first organic film, the thin film for a first electrontransport layer, and the thin film for a first buffer layer,respectively, on the substrate 210 (first photo process).

In this manner, since the first buffer layer 270 a is positioned on theupper portion of the organic compound layer, namely, on the firstelectron transport layer 260 a, the organic compound layer, inparticular, the first electron transport layer 260 a, is prevented frombeing degraded, thus preventing a degradation of the device.

Also, since the first buffer layer 270 a of metal oxide is applied, anenergy barrier between the first electron transport layer 260 a and thecommon electrode can be lowered, enhancing efficiency and a life span.

Here, for example, the first light emitting layer 250 a may be a redlight emitting layer, and the etching may include wet etching, as wellas dry etching. However, the present invention is not limited theretoand the first light emitting layer 250 a may be a green or blue lightemitting layer.

Thereafter, as shown in FIG. 4E, the first photosensitive resin patternis removed.

Thereafter, as shown in FIG. 4F, a second hole injection layer 230 b, asecond hole transport layer 240 b, a second light emitting layer 250 b,a second electron transport layer 260 b, and a second buffer layer 270b, which are formed of a thin film for a second hole injection layer, athin film for a second hole transport layer, a second organic film, athin film for a second electron transport layer, and a thin film for asecond buffer layer, respectively, are formed on the substrate 210through a second photo process which is substantially the same as thefirst photo process as mentioned above.

Here, for example, the second light emitting layer 250 b may be a greenlight emitting layer. However, the present invention is not limitedthereto and when the first light emitting layer 250 a is a red lightemitting layer, the second light emitting layer 250 b may be a bluelight emitting layer, other than a green light emitting layer.

Thereafter, as shown in FIG. 4G, a third hole injection layer 230 c, athird hole transport layer 240 c, a third light emitting layer 250 c, athird electron transport layer 260 c, and a third buffer layer 270 c,which are formed of a thin film for a third hole injection layer, a thinfilm for a third hole transport layer, a third organic film, a thin filmfor a third electron transport layer, and a thin film for a third bufferlayer, respectively, are formed on the substrate 210 through a thirdphoto process which is substantially the same as the first and secondphoto processes as mentioned above. Here, for example, when the firstlight emitting layer 250 a is a red light emitting layer and the secondlight emitting layer 250 b is a green light emitting layer, the thirdlight emitting layer 250 c may be a blue light emitting layer. Also,when the first light emitting layer 250 a is a red light emitting layerand the second light emitting layer 250 b is a blue light emittinglayer, the third light emitting layer 250 c may be a green lightemitting layer. However, the present invention is not limited theretoand the first light emitting layer 250 a, the second light emittinglayer 250 b, and the third light emitting layer 250 c may be configuredas red, green, and blue light emitting layers irrespective of order.

Thereafter, as shown in FIG. 4H, common electrodes 280 a, 280 b, and 280c as cathodes may be formed on the first buffer layer 270 a, the secondbuffer layer 270 b, and the third buffer layer 270 c. Here, the commonelectrodes 280 a, 280 b, and 280 c, which receive a common voltage, maybe made of a reflective conductive material including calcium (Ca),barium (Ba), magnesium (Mg), aluminum (Al), silver (Ag), or the like, ora transparent conductive material such as ITO, IZO, or the like.

In the OLED display device configured as described above, the first gateelectrode connected to the gate line and the first source electrode andthe first drain electrode connected to the data line may constitute afirst switching thin film transistor (TFT) along with the first activelayer. Also, the second gate electrode connected to the first drainelectrode, the second source electrode connected to the driving voltageline, and the second drain electrode connected to the pixel electrode220 may constitute a driving TFT along with the second active layer.

Also, the pixel electrode 220, the light emitting layers 250 a, 250 b,and 250 c, and the common electrodes 280 a, 280 b, and 280 c mayconstitute an OLED, and the mutually overlapping storage electrode anddriving voltage line may constitute a storage capacitor.

FIGS. 5A through 5G are sequential sectional views illustrating a methodfor fabricating an OLED display device according to a third embodimentof the present invention, in which a method for fabricating an OLEDdiode with respect to some pixels is taken as an example.

Although not shown, as mentioned above, in an OLED display deviceaccording to a third embodiment of the present invention, a gate lineincluding a first gate electrode and a storage electrode including asecond gate electrode may be formed on a substrate 310 made of aninsulating material such as transparent glass, plastic, or the like.

A gate insulating layer made of silicon nitride (SiNx), silicon oxide(SiO₂), or the like, may be formed on the gate line including the firstgate electrode and the storage electrode including the second electrode.

A first active layer and a second active layer, made of semiconductor,may be formed on the gate insulating layer. The first active layer andthe second active layer may be positioned on the first gate electrodeand the second gate electrode, respectively.

A data line, a driving voltage line, a first source/drain electrode, anda second source/drain electrode may be formed on an upper portion of thefirst active layer and the second active layer.

A predetermined passivation layer may be formed on the substrate 310 onwhich the data line, the driving voltage line, the first source/drainelectrode, and the second source/drain electrode have been formed.

As shown in FIG. 5A, a pixel electrode 320 and a connecting electrode(not shown) may be formed on the substrate 310 with the passivation filmformed thereon. The pixel electrode 320 and the connecting electrode maybe made of a transparent conductive material such as indium tin oxide(ITO) or a reflective conductive material such as aluminum, silver, oran alloy thereof.

The pixel electrode 320 as an anode may be electrically connected to thesecond drain electrode through a second contact hole, and the connectingelectrode may electrically connect the first drain electrode and thesecond gate electrode through a first contact hole and a third contacthole.

A partition (not shown) may be formed on the substrate 310 with thepixel electrode 320 formed thereon. Here, the partition may encompassthe edges of the pixel electrode 320, like a bank, to define an opening,and may be made of an organic insulating material or an inorganicinsulating material.

An organic compound layer may be formed on the substrate 310. Here, inthe case of the third embodiment of the present invention, unlike thesecond embodiment of the present invention as described above, theorganic compound layer is formed through a lift-off process.

Namely, as shown in FIG. 5A, a photosensitive resin is coated on theentire surface of the substrate 310 with the pixel electrode 320 formedthereon, to form a first photosensitive resin layer 391.

UV light is selectively irradiated to the first photosensitive resinlayer 391 through a certain mask (not shown).

Thereafter, when the first photosensitive resin layer 391 exposedthrough the mask is developed, a first photosensitive resin pattern 390a made of the photosensitive resin remains only at a position other thana position where a first light emitting layer is to be formed as shownin FIG. 5B.

Thereafter, as shown in FIG. 5C, with the first photosensitive resinpattern 390 a remaining, a thin film 331 for a first hole injectionlayer, a thin film 341 for a first hole transport layer, a firstinorganic film 351, a thin film 361 for a first electron transportlayer, and a thin film 371 for a first buffer layer are deposited on thefirst photosensitive resin pattern 390 a.

Here, the thin film 361 for a first electron transport layer may includea thin film for a first electron injection layer, and the thin film 371for a first buffer layer may be made of a 1-2 Group and 12-16 Groupmetal oxide or 3-12 Group transition metal oxide.

Thereafter, as shown in FIG. 5D, the first photosensitive resin pattern390 a is removed through a first lift-off process. Here, the thin filmfor a first hole injection layer, the thin film for a first holetransport layer, the first organic film, the thin film for the firstelectron transport layer, and the thin film for a first buffer layerremaining on the upper portion of the first photosensitive resin pattern390 a are also removed together with the first photosensitive resinpattern 390 a.

As a result, a first hole injection layer 330, a first hole transportlayer 340 a, a first light emitting layer 350 a, a first electrontransport layer 360 a, and a first buffer layer 370 a, which are formedof the thin film for a first hole injection layer, the thin film for afirst hole transport layer, the first organic film, the thin film forthe first electron transport layer, and the thin film for a first bufferlayer, respectively, are formed on the substrate 310.

Here, for example, the first light emitting layer 350 a may be a redlight emitting layer. However, the present invention is not limitedthereto and the first light emitting layer 350 a may be a green or bluelight emitting layer.

Thereafter, as shown in FIG. 5E, a second hole injection layer 330 b, asecond hole transport layer 340 b, a second light emitting layer 350 b,a second electron transport layer 360 b, and a second buffer layer 370b, which are formed of a thin film for a second hole injection layer, athin film for a second hole transport layer, a second organic film, athin film for a second electron transport layer, and a thin film for asecond buffer layer, respectively, are formed on the substrate 310through a second lift-off process which is substantially the same as thefirst lift-off process as mentioned above.

Here, for example, the second light emitting layer 350 b may be a greenlight emitting layer. However, the present invention is not limitedthereto and when the first light emitting layer 350 a is a red lightemitting layer, the second light emitting layer 350 b may be a bluelight emitting layer, other than a green light emitting layer.

Thereafter, as shown in FIG. 5F, a third hole injection layer 330 c, athird hole transport layer 340 c, a third light emitting layer 350 c, athird electron transport layer 360 c, and a third buffer layer 370 c,which are formed of a thin film for a third hole injection layer, a thinfilm for a third hole transport layer, a third organic film, a thin filmfor a third electron transport layer, and a thin film for a third bufferlayer, respectively, are formed on the substrate 310 through a thirdlift-off process which is substantially the same as the first and secondlift-off processes as mentioned above.

Here, for example, when the first light emitting layer 350 a is a redlight emitting layer and the second light emitting layer 350 b is agreen light emitting layer, the third light emitting layer 350 c may bea blue light emitting layer. Also, when the first light emitting layer350 a is a red light emitting layer and the second light emitting layer350 b is a blue light emitting layer, the third light emitting layer 350c may be a green light emitting layer. However, the present invention isnot limited thereto and the first light emitting layer 350 a, the secondlight emitting layer 350 b, and the third light emitting layer 350 c maybe configured as red, green, and blue light emitting layers irrespectiveof order.

Thereafter, as shown in FIG. 5G, common electrodes 380 a, 380 b, and 380c as cathodes may be formed on the first light emitting layer 350 a, thesecond light emitting layer 350 b, and the third light emitting layer350 c. Here, the common electrodes 380 a, 380 b, and 380 c, whichreceive a common voltage, may be made of a reflective conductivematerial including calcium (Ca), barium (Ba), magnesium (Mg), aluminum(Al), silver (Ag), or the like, or a transparent conductive materialsuch as ITO, IZO, or the like.

In the OLED display device configured as described above, the first gateelectrode connected to the gate line and the first source electrode andthe first drain electrode connected to the data line may constitute afirst switching thin film transistor (TFT) along with the first activelayer. Also, the second gate electrode connected to the first drainelectrode, the second source electrode connected to the driving voltageline, and the second drain electrode connected to the pixel electrode320 may constitute a driving TFT along with the second active layer.

Also, the pixel electrode 320, the light emitting layers 350 a, 350 b,and 350 c, and the common electrodes 380 a, 380 b, and 380 c mayconstitute an OLED, and the mutually overlapping storage electrode anddriving voltage line may constitute a storage capacitor.

Meanwhile, organic substances whose efficiency and life span are rapidlyreduced after the photo process is performed are included in the organiccompound layer. For example, in the case of a blue light emitting layer,device efficiency tends to be reduced from about 5.3 cd/A to 2.0 cd/Aafter a photo process based on 1000 nit.

For example, referring to FIG. 6, there is an organic substance whoselife span is rapidly reduced after a photo process exists, which leadsto a reduction in efficiency and life span of the LED display device.

Thus, in case of a fourth embodiment of the present invention, twopixels among red, green, and blue pixels are patterned through alift-off process, while the other remaining one pixel is deposited to beformed without patterning, to thus simplify the process and increaseefficiency. This will be described in detail with reference to theaccompanying drawings.

FIGS. 7A through 7K are sequential sectional views illustrating a methodfor fabricating an OLED display device according to a fourth embodimentof the present invention, in which a method for fabricating an OLEDdiode with respect to some pixels is taken as an example.

Although not shown, as mentioned above, in an OLED display deviceaccording to a third embodiment of the present invention, a gate lineincluding a first gate electrode and a storage electrode including asecond gate electrode may be formed on a substrate 410 made of aninsulating material such as transparent glass, plastic, or the like.

A gate insulating layer made of silicon nitride (SiNx), silicon oxide(SiO₂), or the like, may be formed on the gate line including the firstgate electrode and the storage electrode including the second electrode.

A first active layer and a second active layer, made of semiconductor,may be formed on the gate insulating layer. The first active layer andthe second active layer may be positioned on the first gate electrodeand the second gate electrode, respectively.

A data line, a driving voltage line, a first source/drain electrode, anda second source/drain electrode may be formed on an upper portion of thefirst active layer and the second active layer.

A predetermined passivation layer may be formed on the substrate 410 onwhich the data line, the driving voltage line, the first source/drainelectrode, and the second source/drain electrode have been formed.

As shown in FIG. 7A, a pixel electrode 420 and a connecting electrode(not shown) may be formed on the substrate 410 with the passivation filmformed thereon. The pixel electrode 420 and the connecting electrode maybe made of a transparent conductive material such as indium tin oxide(ITO) or a reflective conductive material such as aluminum, silver, oran alloy thereof.

The pixel electrode 420 as an anode may be electrically connected to thesecond drain electrode through a second contact hole, and the connectingelectrode may electrically connect the first drain electrode and thesecond gate electrode through a first contact hole and a third contacthole.

A partition (not shown) may be formed on the substrate 410 with thepixel electrode 420 formed thereon. Here, the partition may encompassthe edges of the pixel electrode 420, like a bank, to define an opening,and may be made of an organic insulating material or an inorganicinsulating material.

An organic compound layer may be formed on the substrate 410. Here, inthe case of the fourth embodiment of the present invention, two pixelsamong red, green, and blue pixels are patterned through a lift-offprocess, while the other remaining one pixel is deposited to be formedwithout patterning, to form the organic compound layer.

Namely, as shown in FIG. 7A, a hole injection layer 430 and a holetransport layer 440 are formed on the substrate 410 with the pixelelectrode 420 formed thereon.

As mentioned above, the hole injection layer 430 may facilitateinjection of holes from the pixel electrode 420, and the hole transportlayer 440 serves to allow holes to be transported to the light emittinglayer.

Thereafter, as shown in FIG. 7B, a photosensitive resin is coated on theentire surface of the substrate 410 with the hole injection layer 430and the hole transport layer 440 formed thereon, to form a firstphotosensitive resin layer 491.

UV light is selectively irradiated to the first photosensitive resinlayer 491 through a certain mask (not shown).

Thereafter, when the first photosensitive resin layer 491 exposedthrough the mask is developed, a first photosensitive resin pattern 490a made of the photosensitive resin remains only at a position other thana position where a first light emitting layer is to be formed as shownin FIG. 7C.

Thereafter, as shown in FIG. 7D, with the first photosensitive resinpattern 490 a remaining, a first organic film 451 is deposited thereon.

Thereafter, as shown in FIG. 7E, the first photosensitive resin pattern490 a is removed through a first lift-off process. Here, the firstorganic film 451 remaining on the upper portion of the firstphotosensitive resin pattern 490 a is also removed together with thefirst photosensitive resin pattern 490 a.

As a result, a first light emitting layer 450 a formed of the firstorganic film is formed on the substrate 410.

Here, for example, the first light emitting layer 450 a may be a redlight emitting layer. However, the present invention is not limitedthereto and the first light emitting layer 450 a may be a green or bluelight emitting layer.

As shown in FIG. 7F, a second photosensitive resin layer 492 may beformed by applying a photosensitive resin to the entire surface of thesubstrate 410 with the first light emitting layer 450 a formed thereonin the substantially same manner.

And then, UV light is selectively irradiated to the secondphotosensitive resin layer 492 through a certain mask (not shown).

Thereafter, when the second photosensitive resin layer 492 exposedthrough the mask is developed, a second photosensitive resin pattern 490b made of the photosensitive resin remains only at a position other thana position where a second light emitting layer is to be formed as shownin FIG. 7G.

Thereafter, as shown in FIG. 7H, with the second photosensitive resinpattern 490 b remaining, a second organic film 452 is deposited thereon.

Thereafter, as shown in FIG. 7I, the second photosensitive resin pattern490 b is removed through second first lift-off process. Here, the secondorganic film 452 remaining on the upper portion of the secondphotosensitive resin pattern 490 b is also removed together with thesecond photosensitive resin pattern 490 b.

As a result, a second light emitting layer 450 b formed of the secondorganic film is formed on the substrate 410.

Here, for example, the second emitting layer 450 b may be a green lightemitting layer. However, the present invention is not limited theretoand when the first light emitting layer 450 a is a red light emittinglayer, the second light emitting layer 450 b may be a blue lightemitting layer, other than a green light emitting layer.

As shown in FIG. 7J, a third organic film is deposited on the entiresurface of the substrate 410 with the first light emitting layer 450 aand the second light emitting layer 450 b formed thereon, to form athird light emitting layer 450 c.

Here, the third light emitting layer 450 c may be formed with a certainthickness on upper portions of the first light emitting layer 450 a andthe second light emitting layer 450 b as well as between the first lightemitting layer 450 a and the second light emitting layer 450 b.

Here, for example, when the first light emitting layer 450 a is a redlight emitting layer and the second light emitting layer 450 b is agreen light emitting layer, the third light emitting layer 450 c may bea blue light emitting layer. Also, when the first light emitting layer450 a is a red light emitting layer and the second light emitting layer450 b is a blue light emitting layer, the third light emitting layer 450c may be a green light emitting layer. However, the present invention isnot limited thereto and the first light emitting layer 450 a, the secondlight emitting layer 450 b, and the third light emitting layer 450 c maybe configured as red, green, and blue light emitting layers irrespectiveof order.

Thereafter, as shown in FIG. 7K, an electron transport layer 460 and acommon electrode 480 as a cathode are formed on the substrate 410 onwhich the first light emitting layer 450 a, the second light emittinglayer 450 b, and the third light emitting layer 450 c have been formed.

Here, the electron transport layer 460 may include an electron injectionlayer. The common electrode 480, which receives a common voltage, may bemade of a reflective conductive material including calcium (Ca), barium(Ba), magnesium (Mg), aluminum (Al), silver (Ag), or the like, or atransparent conductive material.

In the OLED display device configured as described above, the first gateelectrode connected to the gate line and the first source electrode andthe first drain electrode connected to the data line may constitute afirst switching thin film transistor (TFT) along with the first activelayer. Also, the second gate electrode connected to the first drainelectrode, the second source electrode connected to the driving voltageline, and the second drain electrode connected to the pixel electrode220 may constitute a driving TFT along with the second active layer.

Also, the pixel electrode 420, the light emitting layers 450 a, 450 b,and 450 c, and the common electrode 480 may constitute an OLED, and themutually overlapping storage electrode and driving voltage line mayconstitute a storage capacitor.

In this manner, for example, when the first light emitting layer 450 a,the second light emitting layer 450 b, and the third light emittinglayer 450 c are a red light emitting layer, a green light emittinglayer, and a blue light emitting layer, respectively, the red lightemitting layer and the green light emitting layer are patterned througha lift-off process and the blue light emitting layer may be commonlyformed on the entire surface.

However, the present invention is not limited thereto. Namely, the greenlight emitting layer and the blue light emitting layer may be patternedthrough a lift-off process while the red light emitting layer may becommonly formed on the entire surface, or the red light emitting layerand the blue light emitting layer may be patterned through a lift-offprocess while the green light emitting layer may be commonly formed onthe entire surface.

FIG. 8 is a sectional view showing another example of an OLED displaydevice fabricated according to the fourth embodiment of the presentinvention illustrated in FIGS. 7A through 7K, in which a first organicfilm is deposited on the entire surface of the substrate 410 with thesecond light emitting layer 450 b and the third light emitting layer 450c formed thereon, to from the first light emitting layer 450 a.

Here, the first light emitting layer 450 a is formed with a certainthickness even on upper portions of the second light emitting layer 450b and the third light emitting layer 450 c, as well as between thesecond light emitting layer 450 b and the third light emitting layer 450c.

FIG. 9 is a sectional view showing another example of an OLED displaydevice fabricated according to the fourth embodiment of the presentinvention illustrated in FIGS. 7A through 7K, in which a secondinorganic film is deposited on the entire surface of the substrate 410with the first light emitting layer 450 a and the third light emittinglayer 450 c formed thereon, to form the second light emitting layer 450b.

Here, the second light emitting layer 450 b is formed with a certainthickness even on upper portions of the first light emitting layer 450 aand the third light emitting layer 450 c, as well as between the firstlight emitting layer 450 a and the third light emitting layer 450 c.

Meanwhile, damage to an organic compound layer due to a photo processmay be prevented according to other methods than those of the second andthird embodiments of the present invention. Namely, an organic compoundlayer may be protected against a photo process by patterning the organiccompound layer by using a cathode as a mask. This will be described indetail according to fifth and sixth embodiments of the presentinvention.

FIGS. 10A through 10H are sequential sectional views illustrating amethod for fabricating an OLED display device according to a fifthembodiment of the present invention.

Although not shown, in an OLED display device according to a fifthembodiment of the present invention, a gate line including a first gateelectrode and a storage electrode including a second gate electrode maybe formed on a substrate 510 made of an insulating material such astransparent glass, plastic, or the like.

A gate insulating layer made of silicon nitride (SiNx), silicon oxide(SiO₂), or the like, may be formed on the gate line including the firstgate electrode and the storage electrode including the second electrode.

A first active layer and a second active layer, made of semiconductor,may be formed on the gate insulating layer. The first active layer andthe second active layer may be positioned on the first gate electrodeand the second gate electrode, respectively.

A data line, a driving voltage line, a first source/drain electrode, anda second source/drain electrode may be formed on an upper portion of thefirst active layer and the second active layer.

A predetermined passivation layer may be formed on the substrate 510 onwhich the data line, the driving voltage line, the first source/drainelectrode, and the second source/drain electrode have been formed.

As shown in FIG. 10A, a pixel electrode 520 and a connecting electrode(not shown) may be formed on the substrate 510 with the passivation filmformed thereon. The pixel electrode 520 and the connecting electrode maybe made of a transparent conductive material such as indium tin oxide(ITO) or a reflective conductive material such as aluminum, silver, oran alloy thereof.

The pixel electrode 520 as an anode may be electrically connected to thesecond drain electrode through a second contact hole, and the connectingelectrode may electrically connect the first drain electrode and thesecond gate electrode through a first contact hole and a third contacthole.

A partition (not shown) may be formed on the substrate 510 with thepixel electrode 520 formed thereon. Here, the partition may encompassthe edges of the pixel electrode 520, like a bank, to define an opening,and may be made of an organic insulating material or an inorganicinsulating material.

An organic compound layer may be formed on the substrate 510.

Here, the organic compound layer may have a multilayer structureincluding an auxiliary layer in order to enhance luminous efficiency ofa light emitting layer that emits light, besides the light emittinglayer. The auxiliary layer may include an electron transport layer and ahole transport layer for balancing electrons and holes and an electroninjection layer and a hole injection layer for strengthening injectionof electrons and holes.

Namely, as shown in FIG. 10B, a thin film 531 for a first hole injectionlayer, a thin film 541 for a first hole transport layer, a first organicfilm 551, a thin film 561 for a first electron transport layer, and afirst conductive film 581 are sequentially deposited on the substrate510 with the pixel electrode 520 formed thereon.

Here, the thin film 561 for a first electron transport layer may includea thin film for a first electron injection layer, and the firstconductive film 581 may be made of a reflective conductive materialincluding calcium (Ca), barium (Ba), magnesium (Mg), aluminum (Al),silver (Ag), or the like, or a transparent conductive material such asITO, IZO, or the like.

Thereafter, as shown in FIG. 10C, a photosensitive resin is coated onthe entire surface of the substrate 510, on which the thin film 531 fora first hole injection layer, the thin film 541 for a first holetransport layer, the first organic film 551, the thin film 561 for afirst electron transport layer, and the first conductive film 581 havebeen deposited, to form a first photosensitive resin layer 591.

Thereafter, UV rays are selectively irradiated to the firstphotosensitive resin layer 591 through a certain mask M.

Thereafter, when the first photosensitive resin layer 591 exposedthrough the mask M is developed, a first photosensitive resin pattern590 a made of the photosensitive resin remains only at a position wherea first light emitting layer is to be formed as shown in FIG. 10D.

Here, the first photosensitive resin pattern 590 a may be patterned tohave at least the same width as that of the underlying pixel electrode520 in consideration of an alignment error of the mask M and otherprocessing errors.

Thereafter, as shown in FIG. 10E, when a partial region of firstconductive film formed under the first photosensitive resin pattern 590a is selectively etched by using the first photosensitive resin pattern590 a as a mask, a first common electrode 580 a formed of the firstconductive film is formed at a position where the first light emittinglayer is to be formed.

Here, the etching may include wet etching as well as dry etching.

Thereafter, as shown in FIG. 10F, a remnant of the first photosensitiveresin pattern is removed through ashing, stripping, or the like, andhere, as partial regions of the thin film for a first hole injectionlayer, the thin film for a first hole transport layer, the first organicfilm, and the thin film for a first electron transport layer exposedthereunder are selectively removed by using the first common electrode580 a as a mask, a first hole injection layer 530 a, a first holetransport layer 540 a, a first light emitting layer 550 a, and a firstelectron transport layer 560 a, which are formed of the thin film for afirst hole injection layer, the thin film for a first hole transportlayer, the first organic film, and the thin film for a first electrontransport layer, respectively, are formed (a first photo process).

In this manner, since the first common electrode 580 a is positioned asa barrier layer on an upper portion of the organic compound layer,namely, on the first electron transport layer 560 a, the organiccompound layer, in particular, the first electron transport layer 560 a,can be prevented from being degraded during the photo process, thuspreventing a degradation of the device.

Here, the first light emitting layer 550 a may be a red light emittinglayer, but the present invention is not limited thereto and the firstlight emitting layer 550 a may be a green or blue light emitting layer.

Next, as shown in FIG. 10G, a second hole injection layer 530 b, asecond hole transport layer 540 b, a second light emitting layer 550 b,a second electron transport layer 560 b, and a second common electrode580 b, which are formed of a thin film for a second hole injectionlayer, a thin film for a second hole transport layer, a second organicfilm, a thin film for a second electron transport layer, and a secondconductive film, respectively, are formed on the substrate 510 through asecond photo process which is substantially the same as the first photoprocess as mentioned above.

Here, the second conductive film may be made of a reflective conductivematerial including calcium (Ca), barium (Ba), magnesium (Mg), aluminum(Al), silver (Ag), or the like, or a transparent conductive materialsuch as ITO, IZO, or the like.

Here, for example, the second light emitting layer 550 b may be a greenlight emitting layer. However, the present invention is not limitedthereto and when the first light emitting layer 550 a is a red lightemitting layer, the second light emitting layer 550 b may be a bluelight emitting layer, other than a green light emitting layer.

Thereafter, as shown in FIG. 10H, a third hole injection layer 530 c, athird hole transport layer 540 c, a third light emitting layer 550 c, athird electron transport layer 560 c, and a third common electrode 580c, which are formed of a thin film for a third hole injection layer, athin film for a third hole transport layer, a third organic film, a thinfilm for a third electron transport layer, and a third conductive film,respectively, are formed on the substrate 510 through a third photoprocess which is substantially the same as the first and second photoprocesses as mentioned above.

Here, the third conductive film may be made of a reflective conductivematerial including calcium (Ca), barium (Ba), magnesium (Mg), aluminum(Al), silver (Ag), or the like, or a transparent conductive materialsuch as ITO, IZO, or the like.

Here, for example, when the first light emitting layer 550 a is a redlight emitting layer and the second light emitting layer 550 b is agreen light emitting layer, the third light emitting layer 550 c may bea blue light emitting layer. Also, when the first light emitting layer550 a is a red light emitting layer and the second light emitting layer550 b is a blue light emitting layer, the third light emitting layer 550c may be a green light emitting layer. However, the present invention isnot limited thereto and the first light emitting layer 550 a, the secondlight emitting layer 550 b, and the third light emitting layer 550 c maybe configured as red, green, and blue light emitting layers irrespectiveof order.

In the OLED display device configured as described above, the first gateelectrode connected to the gate line and the first source electrode andthe first drain electrode connected to the data line may constitute afirst switching thin film transistor (TFT) along with the first activelayer. Also, the second gate electrode connected to the first drainelectrode, the second source electrode connected to the driving voltageline, and the second drain electrode connected to the pixel electrode520 may constitute a driving TFT along with the second active layer.

Also, the pixel electrode 520, the light emitting layers 550 a, 550 b,and 550 c, and the common electrodes 580 a, 580 b, and 580 c mayconstitute an OLED, and the mutually overlapping storage electrode anddriving voltage line may constitute a storage capacitor.

Here, in the OLED display device according to the fifth embodiment ofthe present invention, the organic compound layer and the commonelectrodes are patterned at intervals between neighboring pixels, butthe present invention is not limited thereto.

FIGS. 11A through 11H are sequential sectional views illustrating amethod for fabricating an OLED display device according to a sixthembodiment of the present invention, in which a method for fabricatingan OLED diode with respect to some pixels is taken as an example.

In this case, the OLED display device according to a sixth embodiment ofthe present invention has the same configuration as that of the fifthembodiment of the present invention, except that the organic compoundlayer and the common electrodes are patterned to be in contact with eachother between neighboring pixels.

Although not shown, in an OLED display device according to the sixthembodiment of the present invention, a gate line including a first gateelectrode and a storage electrode including a second gate electrode maybe formed on a substrate 610 made of an insulating material such astransparent glass, plastic, or the like.

A gate insulating layer made of silicon nitride (SiNx), silicon oxide(SiO₂), or the like, may be formed on the gate line including the firstgate electrode and the storage electrode including the second electrode.

A first active layer and a second active layer, made of semiconductor,may be formed on the gate insulating layer. The first active layer andthe second active layer may be positioned on the first gate electrodeand the second gate electrode, respectively.

A data line, a driving voltage line, a first source/drain electrode, anda second source/drain electrode may be formed on an upper portion of thefirst active layer and the second active layer.

A predetermined passivation layer may be formed on the substrate 610 onwhich the data line, the driving voltage line, the first source/drainelectrode, and the second source/drain electrode have been formed.

As shown in FIG. 11A, a pixel electrode 620 and a connecting electrode(not shown) may be formed on the substrate 610 with the passivation filmformed thereon. The pixel electrode 620 and the connecting electrode maybe made of a transparent conductive material such as indium tin oxide(ITO) or a reflective conductive material such as aluminum, silver, oran alloy thereof.

The pixel electrode 620 as an anode may be electrically connected to thesecond drain electrode through a second contact hole, and the connectingelectrode may electrically connect the first drain electrode and thesecond gate electrode through a first contact hole and a third contacthole.

A partition (not shown) may be formed on the substrate 610 with thepixel electrode 620 formed thereon. Here, the partition may encompassthe edges of the pixel electrode 620, like a bank, to define an opening,and may be made of an organic insulating material or an inorganicinsulating material.

An organic compound layer may be formed on the substrate 610.

Here, the organic compound layer may have a multilayer structureincluding an auxiliary layer in order to enhance luminous efficiency ofa light emitting layer that emits light, besides the light emittinglayer. The auxiliary layer may include an electron transport layer and ahole transport layer for balancing electrons and holes and an electroninjection layer and a hole injection layer for strengthening injectionof electrons and holes.

Namely, as shown in FIG. 11B, a thin film 631 for a first hole injectionlayer, a thin film 641 for a first hole transport layer, a first organicfilm 651, a thin film 661 for a first electron transport layer, and afirst conductive film 681 are sequentially deposited on the substrate610 with the pixel electrode 620 formed thereon.

Here, the thin film 661 for a first electron transport layer may includea thin film for a first electron injection layer, and the firstconductive film 681 may be made of a reflective conductive materialincluding calcium (Ca), barium (Ba), magnesium (Mg), aluminum (Al),silver (Ag), or the like, or a transparent conductive material such asITO, IZO, or the like.

Thereafter, as shown in FIG. 11C, a photosensitive resin is coated onthe entire surface of the substrate 610, on which the thin film 631 fora first hole injection layer, the thin film 641 for a first holetransport layer, the first organic film 651, the thin film 661 for afirst electron transport layer, and the first conductive film 681 havebeen deposited, to form a first photosensitive resin layer 691.

Thereafter, UV rays are selectively irradiated to the firstphotosensitive resin layer 691 through a certain mask M.

Thereafter, when the first photosensitive resin layer 691 exposedthrough the mask M is developed, a first photosensitive resin pattern690 a made of the photosensitive resin remains only at a position wherea first light emitting layer is to be formed as shown in FIG. 11D.

Here, the first photosensitive resin pattern 690 a may be patterned suchthat the organic compound layer and a common electrode are patterned tobe in contact with each other between neighboring pixels.

Thereafter, as shown in FIG. 11E, when a partial region of firstconductive film formed under the first photosensitive resin pattern 690a is selectively etched by using the first photosensitive resin pattern690 a as a mask, a first common electrode 680 a formed of the firstconductive film is formed at a position where the first light emittinglayer is to be formed.

Here, the etching may include wet etching as well as dry etching.

Thereafter, as shown in FIG. 11F, a remnant of the first photosensitiveresin pattern is removed through ashing, stripping, or the like, andhere, as partial regions of the thin film for a first hole injectionlayer, the thin film for a first hole transport layer, the first organicfilm, and the thin film for a first electron transport layer exposedthereunder are selectively removed by using the first common electrode680 a as a mask, a first hole injection layer 630 a, a first holetransport layer 640 a, a first light emitting layer 650 a, and a firstelectron transport layer 660 a, which are formed of the thin film for afirst hole injection layer, the thin film for a first hole transportlayer, the first organic film, and the thin film for a first electrontransport layer, respectively, are formed (a first photo process).

In this manner, since the first common electrode 680 a is positioned asa barrier layer on an upper portion of the organic compound layer,namely, on the first electron transport layer 660 a, the organiccompound layer, in particular, the first electron transport layer 660 a,can be prevented from being degraded during the photo process, thuspreventing a degradation of the device.

Here, the first light emitting layer 650 a may be a red light emittinglayer, but the present invention is not limited thereto and the firstlight emitting layer 650 a may be a green or blue light emitting layer.

Next, as shown in FIG. 11G, a second hole injection layer 630 b, asecond hole transport layer 640 b, a second light emitting layer 650 b,a second electron transport layer 660 b, and a second common electrode680 b, which are formed of a thin film for a second hole injectionlayer, a thin film for a second hole transport layer, a second organicfilm, a thin film for a second electron transport layer, and a secondconductive film, respectively, are formed on the substrate 610 through asecond photo process which is substantially the same as the first photoprocess as mentioned above.

Here, the second conductive film may be made of a reflective conductivematerial including calcium (Ca), barium (Ba), magnesium (Mg), aluminum(Al), silver (Ag), or the like, or a transparent conductive materialsuch as ITO, IZO, or the like.

Here, for example, the second light emitting layer 650 b may be a greenlight emitting layer. However, the present invention is not limitedthereto and when the first light emitting layer 650 a is a red lightemitting layer, the second light emitting layer 650 b may be a bluelight emitting layer, other than a green light emitting layer.

Thereafter, as shown in FIG. 11H, a third hole injection layer 630 c, athird hole transport layer 640 c, a third light emitting layer 650 c, athird electron transport layer 660 c, and a third common electrode 680c, which are formed of a thin film for a third hole injection layer, athin film for a third hole transport layer, a third organic film, a thinfilm for a third electron transport layer, and a third conductive film,respectively, are formed on the substrate 610 through a third photoprocess which is substantially the same as the first and second photoprocesses as mentioned above.

Here, the third conductive film may be made of a reflective conductivematerial including calcium (Ca), barium (Ba), magnesium (Mg), aluminum(Al), silver (Ag), or the like, or a transparent conductive materialsuch as ITO, IZO, or the like.

Here, for example, when the first light emitting layer 650 a is a redlight emitting layer and the second light emitting layer 650 b is agreen light emitting layer, the third light emitting layer 650 c may bea blue light emitting layer. Also, when the first light emitting layer650 a is a red light emitting layer and the second light emitting layer650 b is a blue light emitting layer, the third light emitting layer 650c may be a green light emitting layer. However, the present invention isnot limited thereto and the first light emitting layer 650 a, the secondlight emitting layer 650 b, and the third light emitting layer 650 c maybe configured as red, green, and blue light emitting layers irrespectiveof order.

In the OLED display device configured as described above, the first gateelectrode connected to the gate line and the first source electrode andthe first drain electrode connected to the data line may constitute afirst switching thin film transistor (TFT) along with the first activelayer. Also, the second gate electrode connected to the first drainelectrode, the second source electrode connected to the driving voltageline, and the second drain electrode connected to the pixel electrode620 may constitute a driving TFT along with the second active layer.

Also, the pixel electrode 620, the light emitting layers 650 a, 650 b,and 650 c, and the common electrodes 680 a, 680 b, and 680 c mayconstitute an OLED, and the mutually overlapping storage electrode anddriving voltage line may constitute a storage capacitor.

As the present invention may be embodied in several forms withoutdeparting from the characteristics thereof, it should also be understoodthat the above-described embodiments are not limited by any of thedetails of the foregoing description, unless otherwise specified, butrather should be construed broadly within its scope as defined in theappended claims, and therefore all changes and modifications that fallwithin the metes and bounds of the claims, or equivalents of such metesand bounds are therefore intended to be embraced by the appended claims.

What is claimed is:
 1. A method for fabricating an organic lightemitting diode (OLED) display device, the method comprising: forming aplurality of first electrodes on a substrate; forming a first holeinjection layer, a first hole transport layer, a first light emittinglayer, a first electron transport layer, and a first buffer layer in alaminated manner on the substrate through a first photo processincluding a first etching process; forming a second hole injectionlayer, a second hole transport layer, a second light emitting layer, asecond electron transport layer, and a second buffer layer in alaminated manner on the substrate through a second photo processincluding a second etching process; forming a third hole injectionlayer, a third hole transport layer, a third light emitting layer, athird electron transport layer, and a third buffer layer in a laminatedmanner on the substrate through a third photo process including a thirdetching process; and forming a plurality of second electrodesrespectively on the first, second, and third buffer layers, wherein thefirst, second, and third buffer layers are made of a metal oxide.
 2. Themethod of claim 1, wherein the forming of the first hole injectionlayer, the first hole transport layer, the first light emitting layer,the first electron transport layer, and the first buffer layercomprises: depositing a thin film for the first hole injection layer, athin film for the first hole transport layer, a first organic film, athin film for the first electron transport layer, and a thin film forthe first buffer layer on the substrate; applying a photosensitive resinto the entire surface of the substrate with the thin film for the firsthole injection layer, the thin film for the first hole transport layer,the first organic film, the thin film for the first electron transportlayer, and the thin film for the first buffer layer deposited thereon toform a first photosensitive resin layer; exposing and developing thefirst photosensitive resin layer to form a first photosensitive resinpattern made of the photosensitive resin at a position where the firstlight emitting layer is to be formed; and selectively etching the thinfilm for the first hole injection layer, the thin film for the firsthole transport layer, the first organic film, the thin film for thefirst electron transport layer, and the thin film for the first bufferlayer by using the first photosensitive resin pattern as a mask to formthe first hole injection layer, the first hole transport layer, thefirst light emitting layer, the first electron transport layer, and thefirst buffer layer, respectively, on the substrate.
 3. The method ofclaim 1, wherein the forming of the second hole injection layer, thesecond hole transport layer, the second light emitting layer, the secondelectron transport layer, and the second buffer layer comprises:depositing a thin film for the second hole injection layer, a thin filmfor the second hole transport layer, a second organic film, a thin filmfor the second electron transport layer, and a thin film for the secondbuffer layer on the substrate; applying a photosensitive resin to theentire surface of the substrate with the thin film for the second holeinjection layer, the thin film for the second hole transport layer, thesecond organic film, the thin film for the second electron transportlayer, and the thin film for the second buffer layer deposited thereonto form a second photosensitive resin layer; exposing and developing thesecond photosensitive resin layer to form a second photosensitive resinpattern made of the photosensitive resin at a position where the secondlight emitting layer is to be formed; and selectively etching the thinfilm for the second hole injection layer, the thin film for the secondhole transport layer, the second organic film, the thin film for thesecond electron transport layer, and the thin film for the second bufferlayer by using the second photosensitive resin pattern as a mask to formthe second hole injection layer, the second hole transport layer, thesecond light emitting layer, the second electron transport layer, andthe second buffer layer, respectively, on the substrate.
 4. The methodof claim 1, wherein the forming of the third hole injection layer, thethird hole transport layer, the third light emitting layer, the thirdelectron transport layer, and the third buffer layer comprises:depositing a thin film for the third hole injection layer, a thin filmfor the third hole transport layer, a third organic film, a thin filmfor the third electron transport layer, and a thin film for the thirdbuffer layer on the substrate; applying a photosensitive resin to theentire surface of the substrate with the thin film for the third holeinjection layer, the thin film for the third hole transport layer, thethird organic film, the thin film for the third electron transportlayer, and the thin film for the third buffer layer deposited thereon toform a third photosensitive resin layer; exposing and developing thethird photosensitive resin layer to form a third photosensitive resinpattern made of the photosensitive resin at a position where the thirdlight emitting layer is to be formed; and selectively etching the thinfilm for the third hole injection layer, the thin film for the thirdhole transport layer, the third organic film, the thin film for thethird electron transport layer, and the thin film for the third bufferlayer by using the third photosensitive resin pattern as a mask to formthe third hole injection layer, the third hole transport layer, thethird light emitting layer, the third electron transport layer, and thethird buffer layer, respectively, on the substrate.
 5. The method ofclaim 1, wherein the first, second, and third buffer layers are made ofa 1-2 Group and 12-16 Group metal oxide or 3-12 Group transition metaloxide.
 6. The method of claim 1, wherein the first light emitting layeris formed as any one of red, green, and blue light emitting layers. 7.The method of claim 6, wherein the second light emitting layer is formedas another one of the red, green, and blue light emitting layers.
 8. Themethod of claim 7, wherein the third light emitting layer is formed asthe other remaining one of the red, green, and blue light emittinglayers.
 9. The method of claim 1, wherein the third light emitting layeris formed over one of the first electrodes and between the first lightemitting layer and the second light emitting layer.
 10. The method ofclaim 1, wherein the first photo process, the second photo process andthe third photo process are sequentially performed.